Multilayered flat heat exchanger

ABSTRACT

A multilayered flat heat exchanger, consisting of a plurality of concentrically disposed shells. The spaces between adjacent shells are isolated from each other, and each of such spaces has separate inlet and outlet openings. A heat carrying fluid medium and a fluid to be treated by the medium are passed through alternate spaces between the adjacent shells. Each shell is made of two identical halves, having peripheral ear portions, so that the shell can be easily assembled by seamwelding of the two halves. As a result, the heat exchanger can be readily fabricated by assembling the shell one by one starting from the innermost one.

United States Patent MULTILAYERED FLAT HEAT EXCHANGER 5 Claims, 16 Drawing Figs.

0.5. Ci v 165/166, 29/1573, 126/90, 126/99 Int. CL F28! 3/00 Field of Search in l65/l40,

{56] References Cited UNITED STATES PATENTS 1,823.788 9/l96l Dewoitine l65/l66 3.399.720 9/1968 Doelzet l6S/I66 3,402,764 9/1968 Fairbanks 165/140 X Primary ExaminerAlbert W. Davis, Jr. Attorney-Robert E. Burns ABSTRACT: A multilayered flat heat exchanger, consisting of a plurality of concentrically disposed shells. The spaces between adjacent shells are isolated from each other, and each of such spaces has separate inlet and outlet openings. A heat carrying fluid medium and a fluid to be treated by the medium are passed through alternate spaces between the adjacent shells. Each shell is made of two identical halves, having peripheral ear portions, so that the shell can be easily assembled by seamwelding of the two halves As a result, the heat exchanger can be readily fabricated by assembling the shell one by one starting from the innermost one.

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MULTILAYERED FLAT HEAT EXCHANGER This invention relates to a multilayered flat heat exchanger, and more particularly to a multilayered flat heat exchanger consisting of a plurality of concentrically disposed shells, each having a pair of identical halves, made of heat-conductive material, which heat exchanger is fabricated by assembling the sheik one by one by welding, starting from the innermost shell, while forming separate fluid passages between adjacent shells.

in a known heat exchanger, which has heretofore been used in a heater a cooler, or an evaporator, includes a drum having one or more partition walls, made of heat-conductive material, so that heat energy is transferred through the partition walls from a hot fluid to a cold fluid flowing along the opposite surfaces thereof. The partition walls have been made either in the form of tubes suitable for shell-and-tube type heat exchangen, or in the form of finned plates.

The shell-and-tube type heat exchanger includes a large number of tubes, and a pair of end plates holding opposite ends of the tubes. With such construction, a large efi'ective area for heat exchange can be achieved in a compact form. The manufacture of the shell-and-tube type heat exchanger, however, requires a large amount of man-hours, because each one of the large number of tubes has to be carefully joined to the end plates, respectively. As a result, the heat exchanger of the shell-and-tube type becomes heavy, and needs a considerably large amount of man-hours for transportation and erection.

A heat exchanger with finned plates is lighter and can be assembled more easily than the shell-and-tube type heat exchanger. However, the finned plate type heat exchanger is much bulkier than the shell-and-pipe type heat exchanger, for

. providing a given area available for heat transfer. In other words, in order to provide a heat exchanging capacity of certain magnitude, the finned plate type heat exchanger needs more floorspace than the shell-and-tube type heat exchanger.

Therefore, an object of the present invention is to obviate the aforesaid difficulties of the known heat exchangers, by providing an improved multilayered flat heat exchanger which consists of a plurality of shells, each being made of two halves connected together by seamwelding, while forming multilayered fluid passages between adjacent shells. The multilayered flat heat exchanger of the present invention mitigates the shortcomings of the known shell-and-pipe type heat exchangers and finned plate type heat exchangers, while retaining the advantages thereof.

More particularly, the present invention provides an improved heat exchanger, which comprises a plurality of concentrically disposed flat shells, and high-pressure fluid passages and low-pressure fluid passages which are alternately disposed between adjacent shells. Each of the high-pressure fluid passages is separated from adjacent low-pressure passage or passages by means of the shells, each consisting of two halves. The shells are assembled one by one, starting from the innermost shell, by seamwelding the two halves in the form of a flat drum enclosing the next inner shell, while providing sufficiently wide heat transferring areas for ensuring effective heat transferring function.

With the multilayered, flat heat exchanger consisting of such flat drums, according to the present invention, fluid in the heat exchanger flows in multiple layers along smooth passages, while being suitably dispersed, to that the heatexchanging operation can be carried out at a very high efficiency. The smooth flow of the fluid in the heat exchanger of the invention results in a substantial reduction of scale deposit.

According to one of the important features of the present invention, the use of consecutive seamwelding of the two halves of adjacent shells eliminates the need of any packing material, so that the heat exchanger of the present invention has a high durability, yet it can be manufactured at a low cost.

For a better understanding of the invention, reference is made to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view, with a part in section and a part cut away, illustrating a multilayered flat heat exchanger, embodying the present invention;

FIG. 2 is an elevation of the multilayered flat heat exchanger, illustrating the left-hand half thereof in section;

FIG. 3 is a side view, taken from the right-hand side of the heat exchanger;

FIG. 4 is a plan view of the heat exchanger;

FIG. 5 is an enlarged sectional view, taken along the line V-V of FIG. 2;

FIG. 6 is a fragmentary sectional view, taken along the line Vl--Vl of FIG. 2;

FIGS. 70, 8a, 9a, and are schematic elevational views, illustrating inside construction of different inner shells constituting the heat exchanger of the present invention, respectively;

FIGS. 7b, 8b, 9b, and 10b are horizontal sectional views of the inner shells, taken along the line VIlb-Vllb, VIllb-Vlllb, lXb-IXBb, and Xb-Xb, respectively; and

FIGS. 11a and 11b are a schematic elevational view and a horizontal sectional view along the line Xlb-Xlb, respectively, showing an outer shell.

Like parts are designated by like numerals throughout the drawings.

The heat exchanger of the present invention includes inner and outer shells, which are preferably made of metal sheets with a high corrosion-resistance, such as sheets of stainless steel, titanium, zirconium, or tantalum.

Referring to FIGS. 1 and 7a, a first inner shell 1 of a preferred embodiment of the invention comprises a pair of vertically elongated flat rectangular halves. The top portion of the first inner shell I is suitably cloud. Each half of the first inner shell 1 includes a peripheral ear portion 2. which extends along the entire peripheral edge of the half, so as to facilitate the combination of the two halves by seamwelding of the ear portions thereof. At the opposite ends of the lower edge of the vertically extending shell, a first horizontal inlet opening 5 and a first horizontal outlet opening 6 are formed by assembling corresponding terminal recesses 3 and 4 which are provided on each half of the shell I, as shown in FIGS. 70 and 7b.

A vertically extending partition wall or a central flat portion 8a is disposed along the vertical centerline of the first inner shell 1, so that an inverse-U-shaped recess 7 can be formed in each half of the shell 1 between the ear portion 2 and the central flat portion 8a, which recess 7 extends from the terminal recess 3 for the inlet opening 5 to the terminal recess 4 for the outlet opening 6. A straight ridge 8b is disposed on each of the vertical leg portions of the inverse-U-shaped recess '7. Thereby, two parallel grooves are formed on each of the vertical portions of the inveIse-U-shapcd recess 7.

Referring to FIG. 5, the first inner shell 1 is assembled by sealingly connecting the aforesaid two halves by a suitable means, such as by seamwelding, along the ear portions 2, the central flat portion 8a, and the ridges 8b. The cross section of the inverse-U-shaped recesses 7 is such that when the two halves are thus connected together, there is produced a first inverse-U-shaped passage 9, which extends between the first horizontal inlet opening 6 and the first horizontal outlet opening 7. The horizontal cross section of each leg portion of the first inverse-U-shaped passage 9 comprises a pair of circular passages, as shown in the figure.

A second inner shell [0, as shown in FIGS. Ba and 8b, includes a pair of vertically elongated flat rectangular halves, which are substantially similar to the halves of the first inner shell 10. Each half of the second inner shell II] has a peripheral ear portion 11. Two pairs of terminal recesses are formed on the ear portion ll; namely, a horizontally aligned pair of terminal recesses l2, l3; and a vertically aligned pair of terminal recesses 14, 15. When the two halves of the second inner shell 10 are properly connected together so as to enclose the first inner shell I, the horizontally aligned pair of terminal recesses l2, 13 come in sealing contact with the outer peripheral surface of the first horizontal inlet 5 and the first horizontal outlet 6, respectively, as shown in FIG. 6. Thereby, the inside of the second inner shell is separated from the inside of the first inner shell 1. The vertically aligned terminal recesses l4, l5 constitute a first vertical inlet opening 16 and a first vertical outlet opening 17 (FIG. 2), respectively. in this particular embodiment, the first vertical inlet and outlet openings 16 and 17 are used for feeding and discharging a fluid coolant.

Linear recesses 18 are formed between each of two vertical ridges 19b and vertical parts of the ear portion 11, and between a central flat portion [9a and the two vertical ridges 19b. The central flat portion 190 and the ridges 19b of the second inner shell 10 are formed in a manner similar to those of the first inner shell 1, except that the recesses 18 formed therebetween are not U-shaped but substantially vertically straight and that the horizontal widths of the portion 19a and the ridges 19b of the shell 10 are shorter than those of the shell I. Furthermore. when the two halves of the second inner shell I0 are properly assembled, the central flat portions 19a and the ridges 19b do not abut with each other, as in the case of the first inner shell I, but come in contact with the rear faces of the corresponding central flat portions 80 and the ridge 8b of the first inner shell I, as shown in FIG. 5. When assembled, the linear recesses 18 of the halves form first straight passages 20, each having an annular cross section surrounding the first inverse-U-shaped passage 9, as shown in FIGS. 1 and 2.

The second inner shell I0 is formed by joining the two halves by a suitable means, e.g., by seamwelding the ear portions II, the central flat portions 19a and the ridges 19b. It should be noted here that the distance between the inner edges of the opposing vertical parts of the ear portions ll of the second inner shell 10, or the length L, of FIG. 8b, is longer than the distance between the outer edges of the opposing vertical parts of the ear portions 2 of the first inner shell 1, or the length L, of FIG. 6b.

FIGS. 9:: and 9b illustrate a third inner shell 21 consisting of a pair of vertically elongated flat rectangular halves which are substantially similar to those of the second inner shell 10. Each half of the third inner shell 21 has a peripheral ear portion 22, which includes two pairs of terminal recesses; namely, a vertically aligned pair of terminal recesses 23, 24; and a horizontally aligned pair of terminal recesses 25, 26. When the two halves of the third inner shell 21 are properly connected together so as to enclose the second inner shell 10, the vertically aligned terminal recesses 23 and 24 come in sealing contact with the outer peripheral surface of the first vertical inlet and outlet openings 16 and I7, respectively, as shown in FIG. 2. Thereby, the inside of the third inner shell 21 is separated from the inside of the second inner shell 10. At the same time, the horizontally aligned pair of terminal recesses 25, 26 constitute a second horizontal inlet opening 27 and a second horizontal outlet opening 28, as shown in FIG. 6. The second horizontal inlet and outlet openings 27, 28 are concentrically disposed about the first horizontal inlet and outlet opening 5, 6, respectively, as can be seen from the figure.

A looped recess 29 is formed in each half of the third inner shell 21 between the peripheral ear portion 22 and the central elongated flat portion 300. The horizontal width of the central flat portion 300 of the third inner shell 21 is shorter than that of the central flat portion [9a of the second inner shell 10. When the two halves of the third inner shell 21 are properly assembled, the central tlat portions 300 come in contact with the back, or outer, faces of the corresponding central flat portions I90 of the second inner shell 10, as shown in FIG. 5.

It is important in the flat heat exchanger of the invention that the outer contour of the second inner shell 10 includes a special portion, such as contour portions 140 of FIG. 8, so that the looped recesses in the two halves of the third inner shell 21 are completely blocked at the lower portions thereof by the outer contour 14a of the second inner shell 10, as shown by dotted lines in FIG. 9a. Thereby, when the two halves of the third inner shell 21 are assembled so as to enclose the second inner shell 10, the looped recesses 29 produce a second inverse-U-shaped passage 31, which extends between the second horizontal inlet and outlet openings 27 and 28, as shown in FIGS. 6 and 9a.

In the illustrated embodiment, each vertical portion of the second inverse-U-shaped passage 3l surrounds a pair of vertical portions of the first straight passages 20, and the diameter of the passage 31 becomes considerably large. In order to prevent the passage 31 from deforming or flexing, a pair of outwardly projecting vertical ridges 30b are formed on each half of the third inner shell 21, in parallel with the central flat portion 30a at the bottom of the sloped recess 29.

The two halves of the third inner shell 21 are joined together by a suitable means, for instance, by seamwelding of the ear portions 22 and the central flat portions 300. The distance between the inner edges of the opposing vertical parts of the ear portions 22 of the third inner shell 21, or the length L, of FIG. 9b, is longer than the distance between the outer edges of the opposing vertical parts of the ear portions 11 of the second inner shell 10, or the distance L, of FIG. 8b.

FIGS. 10a and 10b illustrate a fourth inner shell 32 consisting of a pair of vertically elongated flat rectangular halves, which are substantially similar to those of the third inner shell 21. Each half of the fourth inner shell 32 has a peripheral ear portion 33, which includes two pairs of terminal recesses; namely, a horizontally aligned pair of terminal recesses 34, 35; and a vertically aligned pair of tenninal recesses 36, 37. When the two halves of the fourth inner shell 32 are properly connected together so as to enclose the third inner shell 2!, the horizontally aligned terminal recesses 34, 35 come in sealing contact with the outer peripheral surface of the second horizontal inlet and outlet openings 27, 28, respectively, as shown in FlG. 6. Thereby, the inside of the fourth inner shell 32 is separated from the inside of the third inner shell 21. At the same time, the vertically aligned terminal recesses 36, 37 constitute a second vertical inlet opening 38 and a second vertical outlet opening 39, respectively, as shown in FIG. 2. The second vertical inlet and outlet openings 38, 39 are concentri' cally disposed about the first vertical inlet and outlet openings l6, 17, respectively. In this particular embodiment of the in vention, the second vertical inlet and outlet openings 38, 39 are also used for feeding and discharging the fluid coolant, in the same manner as the first vertical inlet and outlet openings l6, 17.

Linear recesses 40 are formed in each of the two halves of the fourth inner shell 32, which extend between the vertically aligned terminal recesses 36 and 37. When the two halves of the shell 32 are properly assembled, so as to enclose the third inner shell 21, the linear recesses 40 constitute a second straight passage 42 extending from the second vertical inlet opening 38 to the second vertical outlet opening 39. In order to prevent the linear recesses 40 from deforming, a pair of inwardly projecting ridges 41 are formed in parallel with the vertical axis passing through the centers of the inlet and outlet openings 38 and 39. In a preferred embodiment, as shown in FIG. 5, the inwardly projected tip portion of each ridge 4] of the fourth inner shell 32 may be kept in contact with the outwardly projected tip portion of each ridge 30b of the third inner shell 21.

A central flat portion 41a is formed in each half of the fourth inner shell 32, in parallel with the ridges 41, as shown in FIGS. 10a and 10b, for the purpose to be described hereinafter.

The two halves of the fourth inner shell 32 are joined together by a suitable means, for instance, by seamwelding of the ear portions 33, after enclosing the third inner shell 2l by the fourth shell 32. The distance between the inner edges of the opposing vertical parts of the ear portions 33 of the fourth inner shell 32, or the length L, of FIG. [0b, is longer than the distance between the outer edges of the opposing vertical parts of the ear portions 22 of the third inner shell 2], or the distance L, of F lG. 9b.

FIGS. I la and 1 lb illustrate an outer shell 43 consisting of a pair of vertically elongated flat rectangular halves which are substantially similar to those of the fourth inner shell 32. Each half of the outer shell 43 has a peripheral ear portion 44, which includes two pairs of terminal recesses; namely, a vertically aligned pair of terminal recesses 45, 46; and a horizontally aligned pdr of terminal recesses 47, 48. When the two halves of the outer shell 43 are properly connected together so as to enclose the fourth inner shell 32, the vertically aligned terminal recesses 45, 46 come in sealing contact with the outer peripheral surfaces of the second vertical inlet and outlet openings 38, 39, respectively, as shown in FIG. 2. Thereby, the inside of the outer shell 43 is separated from the inside of the fourth inner shell 32. At the same time, the horizontally aliped pair of terminal recesses 47, 48 constitute a third horizontal inlet opening 49 and a third horizontal outlet opening 50, as shown in FIGS. 4 and 6. The third horizontal inlet and outlet openings 49, 50 are concentrically disposed about the second horizontal inlet and outlet openings 27, 28, respectively, as can be seen from FIG. 6.

A looped reces 51a is formed in each half of the outer shell 43 between the peripheral ear portion 44 and a central elongated flat portion 52. The horizontal width of the central flat portion 52 is shorter than that of the central flat portion 410 of the fourth inner shell 32. When the two halves of the outer shell 43 are properly assembled, the central flat portions 52 come in contact with the back, or outer, faces of the corresponding central flat portions 41a of the fourth inner shell 32, as shown in FIG. 5.

It is important in the flat heat exchanger of the present invention that the outer contour of the fourth inner shell 32 includes a special portion, such as contour portions 360 of FIG. a, to that the looped recesses 51a of the outer shell 43 are completely blocked at the lower portions thereof by the outer contour 36a of the fourth inner shell 32, as indicated by dotted lines in FIG. 11a. Thereby, when the two halves of the outer shell 43 are assembled so as to enclose the fourth inner shell 32, the looped recesses 51a produce a third inverse-U-shapcd passage SI, which extends between the third horizontal inlet and outlet openings 49 and 50, as shown in FIGS. 6 and Ila.

In order to prevent the third inverse-U-shaped passage Sl from deforming, a pair of vertical ridges 53 are formed on each halfof the outer shell 43, in parallel with the central flat portion 52, so as to extend toward the outside of the outer shell, as shown in FIGS. 3, 4, and 11b.

The two halves of the outer shell 43 are joined together by a suitable means, for instance, by seamwelding of the ear portions 44. The distance between the inner edges of the opposing vertical parts of the ear portion 44 of the outer shell 43, or the length L, of FIG. 11b, is longer than the distance between the outer edges of the opposing vertical parts of the ear portion 33 of the fourth inner shell 32, or the distance L-, of FIG. 10b.

In order to fabricate the heat exchanger of the present invention, the first inner shell I is at first assembled by seamwelding of a pair of halves made by stamping metal sheets in the aforesaid manner. The searnwelding is applied to the ear portions 2, the central flat portion 8a, and the ridges 8b, so that the first inverse-U-shaped passage 9 is formed so as to extend from the first horizontal inlet 5 to the first horizontal outlet 6.

The first inner shell 1 is enclosed by the second inner shell 10 by seamwelding two halves of the latter along the ear portions II. The central flat portions 190 and the ridges 19b of the second inner shell 10 are seamwelded to the outer surfaces of the corresponding central flat portion 8a and the ridges 8b of the first inner shell 1. A plurality of first straight passages 20, e.g., four straight passages in the illustrated embodiment, are formed between the first and the second inner shells, so as to extend from the first vertical inlet 16 to the first vertical outlet I7. Due car should be taken to ensure fluidtight sealing between the outer surface of the first inner shell I and the horizontally aligned pair of tenninal recesses 12, 13 of the second inner shell 10. Ifthere should be any leakage at the terminal recesses l2, 13, the coolant flowing through the first inverse-U-shaped passage 9 will enter into the first straight passages 20, resulting in contamination of the fluid being treated in the heat exchanger.

Similarly, the third inner shell 2] is assembled so as to enclose the second inner shell 10 by seamwelding of the ear portions 22. The central flat portions 300 of the third inner shell 21 are seamwelded to the back surfaces of the corresponding central flat portions 19a of the second inner shell 10, so as to form second inverse-U-shaped passage 31 extending from the second horizontal inlet opening 27 to the second horizontal outlet opening 28. The fluidtight contact between the vertically aligned terminal recesses 23, 24 and the outer surfaces of the second inner shell 10 is critical for the successful fabrication of the heat exchanger of the invention.

Furthermore, the fourth inner shell 32 is assembled so as to enclose the third inner shell 21, by seamwelding of the peripheral ear portions 33 of the two halves, while ensuring fluidtight contact between the horizontally aligned terminal recesses 34, 35 and the outer surfaces of the third inner shell 21. Thereby, the second straight passages 42 are formed between the third inner shell 21 and the fourth inner shell 32, which extend from the second vertical inlet 38 to the second vertical outlet 39.

Finally, the outer shell 43 is assembled by searnwelding of the ear portions 44 of the two halves thereof, so as to enclose fourth inner shell 32, while ensuring lluidtight contact between the vertically aligned terminal receses. 45, 46 and the outer surfaces of the fourth inner shell 32. Thereby, the third inverse-U-shaped passage 5] between the fourth inner shell 32 and the outer shell 43, which extends from the third horizontal inlet opening 49 to the third horizontal outlet opening 50.

It is now apparent that if a fluid to be heat-treated is forced from the lower side of the heat exchanger, as shown by the arrow A of FIG. 1, the fluid enters into the first and second straight passages 20 and 42 through the first and second vertical inlet openings 16 and 38, and flows upward until the fluid is discharged from the heat exchanger at the first and second vertical outlet openings 17 and 39 in a direction as shown by the arrow A of FIG. 1. If a suitable coolant is forced to the left-hand side lower edge of the heat exchanger, as shown by the arrow B of FIG. I, the coolant enters into the first, second and third inverse-U-shaped passages 9, 31, and 51 through the first, second, and third horizontal inlets 5, 27, and 49. The coolant flows along the shape of the passages, while exchanging its heat energy with the fluid flowing in the straight passages through the shell walls, until it is discharged from the heat exchanger at the first, second, and third horizontal outlet openings 6, 28, and 50, in the direction as shown by the arrow B of FIG. I. Thus, the exchange of heat energy between the fluid being treated and the coolant can efficiently be carried out by causing the fluid being treated and the coolant to flow alternately through the aforesaid passages while forming interlaced multilayered streams.

The individual shells can be manufactured at low cost on mass-production basis, simply by forming the halves thereof by stamping metal sheets into the desired shape with a highpressure press. The halves of the shells thus formed can very easily be assembled into the heat exchanger by seamwelding, starting from the innermost or the first inner shell toward the outside, in succession, until the outermost shell is assembled.

The salient features of the present invention can be summarized as follows.

I. The individual shells can be manufactured simply by forming halves of each shell by stamping or pressing metal sheets, and then sealingly seamwelding the halves thus formed, starting from the innermost shell toward the outermost shell in succession. A wide heat exchanging area can be provided when a coolant and a fluid to be treated are forced through the heat exchanger alternately through every other spaces between the adjacent shells.

Thus. the heat exchanger can be formed in a flat shape with multilayered fluid passages. As a result, the heat exchanger of the present invention can be manufactured much smaller and much lighter, as compared with conventional heat exchangers of comparative capacity. For instance, the floor space of a heat exchanger of the invention is about one half and its weight is about one fourth of those of a typical known heat exchanger of equivalent capacity. The multilayered construction ensures high efficiency of heat exchange, despite the reduced size and weight thereof. In short, the heat exchanger of the present invention mitigates the difficulties of both the known shell-and-tube type heat exchanger and the finned plate type heat exchanger, while retaining the advantages of both type heat exchangers. Besides, the heat exchanger of the present invention can be manufactured at a low cost.

2. The multilayered structure, made of highly corrosion-resisting metal sheets, ensures smooth uniform fluid flow therethrough, without causing any heat loss. Besides, the amount of scale deposits can be reduced drastically, as compared with that of known heat exchangers.

3. The use of seamwelding for connecting two halves of each shell completely eliminates the need of packings and tightening bolts. Thus, the number of parts in the heat exchanger is greatly reduced. At the same time, the risk of troubles, such as leakage due to packing breakage, can be completely eliminated. Consequently, a long service life of the heat exchanger can be warranted.

What is claimed is:

l. A multilayered flat heat exchanger, comprising a plurality of concentrically disposed substantially square hollow flat shells, each shell being vertically elongated and made of a pair of identical halves, which halves are joined together so as to enclose a next inwardly adjacent shell with a spacing therefrom, at least one inverse-U-shaped passage being formed within each odd numbered shell, as sequentially counted from the innermost shell, which is referred to as number one, and at least one straight passage being disposed between adjacent inverse-U-shaped passages, each said inverse-U-shaped passage being completely isolated from any of the straight passages and being equipped with an inlet opening and an outlet opening, each said straight passage being completely isolated from any of the inverse-U-shaped passages and being equipped with an inlet opening and an outlet opening, said shells at least including a first shell located at the innermost portion of the heat exchanger and having a horizontal inlet opening slightly projecting outwardly from the periphery of the first shell at one end of the bottom edge thereof, a horizontal outlet opening slightly projecting outwardly from the periphery of the first shell at the opposite end of the bottom edge thereof, and a central partition extending vertically within the shell from the central portion of the bottom edge to the proximity of a top edge of the first shell, so as to define an inverse-U-shaped passage communicating therethrough the horizontal inlet opening with the horizontal outlet opening; at least one even numbered shells, as counted from the innermost shell, each enclosing a next inward shell with a spacing therefrom and having a vertical inlet opening slightly projecting outwardly from the periphery thereof at one end of the vertical center line thereof, a vertical outlet opening slightly projecting outwardly from the periphery thereof at the opposite end of the vertical center line, and a pair of fitting openings formed at opposite ends of the bottom edge of each even numbered shell, said fitting openings sealingly engaging the outer surfaces of the horizontal inlet and outlet openings of the next inward shell, respectively, so as to completely separate the inside of the next inward shell from the space between each even numbered shell and the next inward shell, said space between each even numbered shell and the next inward shell forming a vertical passage communicating therethrough the vertical Inlet opening with the vertical outlet opening, respectively; and at least one odd numbered shells, as counted from the innermost shell, each enclosing a next inside shell with a spacing therefrom and having a horizontal inlet opening slightly projecting outwardly from the periphery thereof at one end of the bottom edge thereof, a horizontal outlet opening slightly projecting outwardly from the periphery thereof at the opposite end of the bottom edge thereof, and a pair of fitting openings formed at opposite ends of a vertical centerline of each odd numbered shell, said fitting openings sealingly engaging the outer surfaces of the vertical inlet and outlet openings of the next inward shell, respectively, so as to completely separate the inside of the next inward shell from the space between each odd numbered shell and the next inward shell, said space between each odd numbered shell and the next inward shell forming an inverse-U-shaped passage communicating therethrough the horizontal inlet opening with the horizontal outlet opening, respectively 2. A multilayered flat heat exchanger according to claim I, wherein each of the two halves of every shell has a peripheral ear portion, so that the two halves can be joined together by seamwelding the halves along the ear portions 3. A multilayered fiat heat exchanger according to claim I, wherein the straight passages carry a heat source fluid, while the inverse-U-shaped passages carry a fluid being treated by the heat source fluid.

4. A multilayered flat heat exchanger according to claim 1, wherein the inverse-U-shaped passages carry a heat source fluid, while the straight passages carry a fluid being treated by the heat source fluid.

5. A multilayered flat heat exchanger according to claim I, wherein the heat exchanger comprises five shells consisting of a first shell having a pair of ridges for vertically bisecting each of the vertical portions of the inverse-U-shaped passage, a second shell having a central flat portion and a pair of ridges for dividing the vertical passage into four vertical sections, a third shell having four outwardly projecting vertical ridges for preventing deformation thereof, a fourth shell having four inwardly projecting vertical ridges, and a fifth shell having four outwardly projecting ridges. 

1. A multilayered flat heat exchanger, comprising a plurality of concentrically disposed substantially square hollow flat shells, each shell being vertically elongated and made of a pair of identical halves, which halves are joined together so as to enclose a next inwardly adjacent shell with a spacing therefrom, at least one inverse-U-shaped passage being formed within each odd numbered shell, as sequentially counted from the innermost shell, which is referred to as number one, and at least one straight passage being disposed between adjacent inverse-U-shaped passages, each said inverse-U-shaped passage being completely isolated from any of the straight passages and being equipped with an inlet opening and an outlet opening, each said straight passage being completely isolated from any of the inverse-Ushaped passages and being equipped with an inlet opening and an outlet opening, said shells at least including a first shell located at the innermost portion of the heat exchanger and having a horizontal inlet opening slightly projecting outwardly from the periphery of the first shell at one end of the bottom edge thereof, a horizontal outlet opening slightly projecting outwardly from the periphery of the first shell at the opposite end of the bottom edge thereof, and a central partition extending vertically within the shell from the central portion of the bottom edge to the proximity of a top edge of the first shell, so as to define an inverse-Ushaped passage communicating therethrough the horizontal inlet opening with the horizontal outlet opening; at least one even numbered shells, as counted from the innermost shell, each enclosing a next inward shell with a spacing therefrom and having a vertical inlet opening slightly projecting outwardly from the periphery thereof at one end of the vertical center line thereof, a vertical outlet opening slightly projecting outwardly from the periphery thereof at the opposite end of the vertical center line, and a pair of fitting openings formed at opposite ends of the bottom edge of each even numbered shell, said fitting openings sealingly engaging the outer surfaces of the horizontal inlet and outlet openings of the next inward shell, respectively, so as to completely separate the inside of the next inward shell from the space between each even numbered shell and the next inward shell, said space between each even numbered shell and the next inward shell forming a vertical passage communicating therethrough the vertical inlet opening with the vertical outlet opening, respectively; and at least one odd numbered shells, as counted from the innermost shell, each enclosing a next inside shell with a spacing therefrom and having a horizontal inlet opening slightly projecting outwardly from the periphery thereof at one end of the bottom edge thereof, a horizontal outlet opening slightly projecting outwardly from the periphery thereof at the opposite end of the bottom edge thereof, and a pair of fitting openings formed at opposite ends of a vertical centerline Of each odd numbered shell, said fitting openings sealingly engaging the outer surfaces of the vertical inlet and outlet openings of the next inward shell, respectively, so as to completely separate the inside of the next inward shell from the space between each odd numbered shell and the next inward shell, said space between each odd numbered shell and the next inward shell forming an inverse-U-shaped passage communicating therethrough the horizontal inlet opening with the horizontal outlet opening, respectively
 2. A multilayered flat heat exchanger according to claim 1, wherein each of the two halves of every shell has a peripheral ear portion, so that the two halves can be joined together by seamwelding the halves along the ear portions
 3. A multilayered flat heat exchanger according to claim 1, wherein the straight passages carry a heat source fluid, while the inverse-U-shaped passages carry a fluid being treated by the heat source fluid.
 4. A multilayered flat heat exchanger according to claim 1, wherein the inverse-U-shaped passages carry a heat source fluid, while the straight passages carry a fluid being treated by the heat source fluid.
 5. A multilayered flat heat exchanger according to claim 1, wherein the heat exchanger comprises five shells consisting of a first shell having a pair of ridges for vertically bisecting each of the vertical portions of the inverse-U-shaped passage, a second shell having a central flat portion and a pair of ridges for dividing the vertical passage into four vertical sections, a third shell having four outwardly projecting vertical ridges for preventing deformation thereof, a fourth shell having four inwardly projecting vertical ridges, and a fifth shell having four outwardly projecting ridges. 